linux-kernel - Re: [PATCH] mmc: meson: initial ocr available by default value

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Date:   Mon, 13 Dec 2021 14:22:25 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     "rong.chen@...ogic.com" <rong.chen@...ogic.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        --to=1131046452 <--to=1131046452@...com>,
        45581586 <45581586@...com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-amlogic <linux-amlogic@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: meson: initial ocr available by default value


On Mon 13 Dec 2021 at 19:50, "rong.chen@...ogic.com" <rong.chen@...ogic.com> wrote:

> Hello,
> If 3.3V always-on power source for vmmc is supplied by hardware boards fixed, don't need regulator in software, so  .dts unnecessary the link between regulator
> and MMC controller vmmc/vqmmc. 

Controllable or not, your vmmc/vqmmc regulators should be described in
DT.

There are several examples of this in arch/arm64/boot/dts/amlogic/*.dts


>
> ------------------------------------------------------------------------------------------------------------------------------------------------------
> rong.chen@...ogic.com
>
>   
>  From: Martin Blumenstingl
>  Date: 2021-12-13 16:00
>  To: Rong Chen
>  CC: Ulf Hansson; Neil Armstrong; Kevin Hilman; Jerome Brunet; --to=1131046452; 45581586; linux-mmc; linux-arm-kernel; linux-amlogic; linux-kernel
>  Subject: Re: [PATCH] mmc: meson: initial ocr available by default value
>  [ EXTERNAL EMAIL ]
>   
>  Hello,
>   
>  On Mon, Dec 13, 2021 at 8:03 AM Rong Chen <rong.chen@...ogic.com> wrote:
>  >
>  > The patch will add a value of ocr supported by the controller,
>  > to specify some of voltage values are supported.
>  Can you please share some details on this topic?
>   
>  We already have many boards upstreamed which work fine without
>  manually setting ocr_avail in the driver.
>  In general there's two types of boards:
>  1) boards where the regulator can switch between different voltages.
>  One example is the Odroid-C2, see meson-gxbb-odroidc2.dts [0]
>  Here we specify:
>    vmmc-supply = <&tflash_vdd>;
>    vqmmc-supply = <&tf_io>;
>  &tflash_vdd is either turned off or at 3.3V when turned on.
>  &tf_io can be either turned off, 1.8V or 3.3V.
>   
>  2) boards where the voltages are fixed.
>  One example is Radxa Zero, see meson-g12a-radxa-zero.dts [1]
>  For the SD card the board uses:
>    vmmc-supply = <&vddao_3v3>;
>    vqmmc-supply = <&vddao_3v3>;
>  (meaning fixed 3.3V always-on power source for both VMMC and VQMMC)
>  and for eMMC the board uses:
>    vmmc-supply = <&vcc_3v3>;
>    vqmmc-supply = <&vcc_1v8>;
>  (meaning: 3.3V always-on power source for vmmc and 1.8V always-on
>  power source for VQMMC)
>   
>  With the information from the regulators the MMC core will
>  automatically detect ocr_avail in Linux.
>  Or in other words: your .dts may be missing the link between regulator
>  and MMC controller vmmc/vqmmc.
>  Can you please double-check this?
>   
>   
>  Best regards,
>  Martin
>   
>   
>  [0]
>  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-gxbb-odroidc2.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n354
>  
>  [1]
>  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/amlogic/meson-g12a-radxa-zero.dts?id=2585cf9dfaaddf00b069673f27bb3f8530e2039c#n333